| DC/DC converter,an interface converter between device and the DC bus in the DC distribution network,is taken as an important role in energy conversion.Traditional DC/DC converters are not suitable for medium and high power applications because of its shortcomings such as high switching stress,low voltage gain and low power density.Therefore,the research on high-gain multilevel DC/DC converters is of great significance.The triangular MMC DC/DC converter is focus as the research object,the topology and its working principle are analyzed and researched,a control strategy is designed,and an experimental circuit is built to verify the correctness of the theory and simulation.First,the topology of the Triangular MMC DC/DC converter and its working principle are analyzed.According to the relationship between the input and output voltages of the sub-modules,the input and output characteristics of the converter are deduced under different duty ratio control modes.Aiming at the large output voltage ripple in the non-interleaved conduction mode,different level interleaved conduction modes are presented,and their working modes are analyzed.By establishing the mathematical model of the converter,the steady-state characteristics of the converter are analyzed in boost and buck modes.Secondly,the control strategy of the triangular MMC DC/DC converter is designed.Aiming at the coupling relationship between the upper and lower capacitor voltages and the inductor current of the triangular MMC DC/DC converter,the reduced-order average model of the circuit is deduced,and the relationship between the output variable of the voltage loop and the current reference value is obtained,independent control of voltage loops at all levels is realized;Based on the decoupled converter model,a voltage and current compensation network is designed to improve the system performance;The closed-loop state space equation is used to analyze the stability of the nonlinear system stability discrimination method.Aiming at the nonlinear and strong coupling characteristics of DC/DC converters,a fuzzy PI control strategy is designed by combining the fuzzy control algorithm and PI control.By selecting the membership function,designing the fuzzy control rules and calculating the quantization factor and scale factor,the real-time tuning of the PI parameters is realized.The above two controls are simulated by MATLAB/simulink software,and the dynamic and steady state performance of the converter and the effectiveness of the control strategy are verified.Finally,an experimental prototype of a triangular MMC DC/DC converter is built.The hardware system design and software system design are analyzed in detail,and the dynamic and steady state performance of the converter is verified experimentally by using the experimental circuit.There are 52 figures,6 tables and 62 references. |
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